How severe is CVE-2018-20023?

CVE-2018-20023 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.

Is CVE-2018-20023 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (83rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2018-20023?

CVE-2018-20023 primarily affects Libvnc Project Libvncserver. In total, 7 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2018-20023?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2018-20023 published?

CVE-2018-20023 was published on 2018-12-19 and last updated on 2026-06-17.

CVE-2018-20023

CVE-2018-20023 is a high-severity vulnerability in Libvnc Project Libvncserver with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-665.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 2% (83rd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-665
Affected product: Libvnc Project Libvncserver
Published: 2018-12-19
Last modified: 2026-06-17

Description

LibVNC before 8b06f835e259652b0ff026898014fc7297ade858 contains CWE-665: Improper Initialization vulnerability in VNC Repeater client code that allows attacker to read stack memory and can be abuse for information disclosure. Combined with another vulnerability, it can be used to leak stack memory layout and in bypassing ASLR

Frequently asked questions

What is CVE-2018-20023?: LibVNC before 8b06f835e259652b0ff026898014fc7297ade858 contains CWE-665: Improper Initialization vulnerability in VNC Repeater client code that allows attacker to read stack memory and can be abuse for information disclosure. Combined with another vulnerability, it can be used to leak stack memory layout and in bypassing ASLR
How severe is CVE-2018-20023?: CVE-2018-20023 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.
Is CVE-2018-20023 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (83rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2018-20023?: CVE-2018-20023 primarily affects Libvnc Project Libvncserver. In total, 7 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2018-20023?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2018-20023 published?: CVE-2018-20023 was published on 2018-12-19 and last updated on 2026-06-17.

References

Affected products (7)

cpe:2.3:a:libvnc_project:libvncserver:*:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:8.0:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:14.04:*:*:*:lts:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:16.04:*:*:*:lts:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:18.04:*:*:*:lts:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:18.10:*:*:*:*:*:*:*

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CVE-2018-20020 — Critical (CVSS 9.8): LibVNC before commit 7b1ef0ffc4815cab9a96c7278394152bdc89dc4d contains heap out-of-bound write vulnerability inside…
CVE-2018-20019 — Critical (CVSS 9.8): LibVNC before commit a83439b9fbe0f03c48eb94ed05729cb016f8b72f contains multiple heap out-of-bound write vulnerabilities…

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